Some automatic transmissions installed in automobiles are configured to change a power-flow path by changing an engagement state of plural friction elements to select a certain gear from among plural gears having different gear ratios.
In some automatic transmissions, a control valve unit incorporating plural electromagnetic control units for changing an oil passage in a hydraulic system for engaging or disengaging the friction elements is integrally located on a lower side of a gear shift mechanism.
In recent years, the number of selectable gears in automatic transmissions has been increased to improve travelling performance and/or fuel-efficiency of an automobile.
In some conventional automatic transmissions, an electric control unit for controlling the control valve unit is located outside of a transmission case.
But this design has a disadvantage of high manufacturing cost in the case where the automatic transmission has a relatively high number of selectable gears, since it requires many lengthy harnesses for connecting the electric control unit to the large number of control valves corresponding to the high number of selectable gears.
One technology for addressing this disadvantage has been developed, in the form of an automatic transmission for an automobile including a harness integrated insulating sheet and an electric control unit located on the upper side of a valve body of a control valve unit immediately beneath a gear shift mechanism. The reference further discloses a plastic protective cover that covers above the electric control unit, and a rotation sensor, oil temperature sensor and oil pressure sensor that are provided in the harness integrated insulating sheet at an outside of the plastic protective cover. One example of such an automatic transmission is described by U.S. Pat. No. 6,530,856.
However, the inventor herein has recognized a disadvantage with such approaches. Specifically, although the automatic transmission described in above reference can shorten the length of harnesses for connecting an electric control unit with electromagnetic control valves, by locating the electric control unit on the upper side of a valve body of a control valve unit immediately beneath a gear shift mechanism via a harness integrated insulating sheet, the electric control unit can experience thermal damage from high temperature oil for cooling the gear shift mechanism dispersed from the gear shift mechanism, which usually contacts the upper surface of the plastic protective cover, thereby decreasing the durability of the electric control unit.
A first aspect of the present invention includes an automatic transmission including a valve body including control valves for hydraulically controlling a friction engaging element provided within said transmission. The automatic transmission may further include an electric control unit located on said valve body for controlling gear shifting of said automatic transmission. The automatic transmission may further include a transmission case having a peripheral wall for at least partially enclosing a gear shift mechanism and an outer wall provided adjacent to said peripheral wall, wherein said electric control unit is located within a containing space surrounded by said peripheral wall, said outer wall and said valve body.
This automatic transmission overcomes at least some of the disadvantages of above reference.
Since an electric control unit is located within a containing space formed by a peripheral wall, an outer wall provided adjacent to the peripheral wall and a valve body, the electric control unit can be located offset forwardly from immediately beneath the gear shift mechanism by utilizing a dead space formed inside of the outer wall of the transmission case. Accordingly, the electric unit can be located in a position where it does not experience heat damage from high temperature oil dispersed from the gear shift mechanism while the electric unit is located inside of the transmission case, thereby, preventing durability decreasing of the electric control unit.
A second aspect of the present invention includes an automatic transmission including a valve body including control valves for hydraulically controlling a friction engaging element provided within said transmission, and an electric control unit located on said valve body for controlling gear shifting of said automatic transmission. The automatic transmission may further include a transmission case having a peripheral wall for at least partially enclosing a gear shift mechanism, an outer wall provided adjacent to said peripheral wall, and a containing space surrounded by said peripheral wall, said outer wall and said valve body such that a shape of said containing space is convex upward, wherein said electric control unit is located within said containing space.
This automatic transmission also overcomes at least some of the disadvantages of above reference.
In an example embodiment, the automatic transmission may further comprise a primary shaft coaxially positioned relative to an engine output shaft and provided in said gear shift mechanism, a secondary shaft extending parallel to and located above and behind said primary shaft, and a differential axis extending parallel to and located below and behind said primary shaft, wherein said valve body is located under said gear shift mechanism, and said containing space is positioned on a forward side of said gear shift mechanism.
In another example embodiment, the automatic transmission further comprises a rotation sensor for detecting a rotation speed of a designated rotating element of said gear shift mechanism, wherein said rotation sensor is integrated with and extending diagonally from said electric control unit.
In another example embodiment, the automatic transmission further comprises a torque convertor, wherein said rotation sensor is spatially positioned intermediate said electric control unit and said torque convertor.
In another example embodiment, the automatic transmission further comprises a manual valve provided in said valve body and moving in conjunction with a shift range changing operation via a shift lever, and a position detecting sensor for detecting a position of said manual valve, wherein said position detecting sensor is integrated with said electric control unit.
As a non limiting example, the manual valve is located parallel with said primary shaft and is configured to move in an axial direction of the primary shaft.
In one example embodiment, the valve body is one of a plurality of valve bodies, and the automatic transmission further comprises a control valve unit including the plurality of valve bodies stacked in an up and down direction. Further, said manual valve is provided in a one of the valve bodies located on a top portion of said control valve unit, and said electric control unit is located on an upper side of said valve body located on the top portion of said control valve unit.
A third aspect of the present invention includes an automatic transmission including a transmission case having a peripheral wall for at least partially enclosing a gear shift mechanism and an outer wall provided adjacent to said peripheral wall. The peripheral wall and outer wall of the transmission case are formed to at least partially define, with a valve body associated with the transmission case, a containing space sized to contain an electric control unit located on the valve body.
In this way, at least some of the disadvantages of the related reference described above are overcome.